This program is concerned with analysis of peptide hormone receptors in testis and ovary, with particular reference to the control of receptor concentration by changes in homologous and heterologous hormones. The recently-described desensitization of adenylate cyclase and steroidogenic responses to gonadotropic hormones is followed by receptor loss, by turnover or processing of the hormone-receptor complex. These processes were further investigated in Leydig cells and ovarian luteal cells to determine the effects of hormone-induced receptor regulation on the responsiveness of the endocrine target cells, and to analyze the mechanism and consequences of target-cell desensitization.